Surface enhanced raman spectroscopy with periodically deformed SERS-active structure

Abstract

An apparatus and related methods for facilitating surface-enhanced Raman spectroscopy (SERS) is described. A SERS-active structure near which a plurality of analyte molecules is disposed is periodically deformed at an actuation frequency. A synchronous measuring device synchronized with the actuation frequency receives Raman radiation scattered from the analyte molecules and generates therefrom at least one Raman signal measurement.

1. An apparatus for facilitating surface-enhanced Raman spectroscopy (SERS), comprising:
 a SERS-active structure near which a plurality of analyte molecules is disposed; 
 an actuation device in actuable communication with the SERS-active structure, the actuation device periodically deforming the SERS-active structure at an actuation frequency; and 
 a synchronous measuring device receiving Raman radiation scattered from the analyte molecules and generating therefrom at least one Raman signal measurement, wherein said synchronous measuring device is synchronized with said actuation frequency. 
 
   
   
     2. The apparatus of  claim 1 , wherein said synchronous measuring device comprises:
 a Raman signal detector receiving said Raman radiation and generating therefrom at least one spectral detection result; and 
 a synchronous detector operating at said actuation frequency, said synchronous detector receiving said at least one spectral detection result and generating therefrom said at least one Raman signal measurement. 
 
   
   
     3. The apparatus of  claim 2 , said at least one spectral detection result varying periodically at the actuation frequency according to said periodic deformations of the SERS-active structure and exhibiting at least one peak value within at least one peak interval of each period thereof, wherein said synchronous detector comprises a phase sensitive detection device that is phase matched to detect said at least one spectral detection result during said at least one peak interval of each period thereof. 
   
   
     4. The apparatus of  claim 2 , said at least one spectral detection result comprising a first spectral magnitude at a first Raman scattering frequency and a second spectral magnitude at a second Raman scattering frequency, each of said first and second spectral magnitudes varying periodically at the actuation frequency according to said periodic deformations of the SERS-active structure and respectively exhibiting at least one peak value within at least one peak interval of each period thereof, wherein said synchronous detector comprises:
 a first phase sensitive detection device phase matched to detect said first spectral magnitude during said at least one peak interval of each period thereof; and 
 a second phase sensitive detection device phase matched to detect said second spectral magnitude during said at least one peak interval of each period thereof. 
 
   
   
     5. The apparatus of  claim 3 , wherein said synchronous detector is embodied in a computer program product stored on a digital computing device that receives said at least one spectral detection result in digital format and provides said at least one Raman signal measurement in digital format. 
   
   
     6. The apparatus of  claim 2 , wherein said at least one spectral detection result is representative of one or more of an energy of said Raman radiation at a single predetermined scattering frequency, an energy of said Raman radiation at a peak scattering frequency, and a combined spectral energy of said Raman radiation across a predetermined range of Raman scattering frequencies. 
   
   
     7. The apparatus of  claim 2 , said Raman signal detector, said Raman radiation, said actuation device, said SERS-active structure, and said plurality of analyte molecules being a first Raman signal detector, first Raman radiation, a first actuation device, a first SERS-active structure, and a first plurality of analyte molecules, respectively, the apparatus further comprising:
 a second SERS-active structure similar to said first SERS-active structure near which a second plurality of analyte molecules is disposed; 
 a second actuation device in actuable communication with the second SERS-active structure, the second actuation device deforming the second SERS-active structure quasistatically relative to said actuation frequency of said first actuation device; 
 a second Raman signal detector receiving second Raman radiation scattered from said second plurality of analyte molecules and generating therefrom a quasistatic spectral detection result; and 
 an optimal deformation detector for providing an optimal deformation level for said second actuation device based at least in part on said spectral detection result from said first Raman signal detector and said at least one Raman signal measurement from said synchronous detection device. 
 
   
   
     8. The apparatus of  claim 7 , wherein said first plurality of analyte molecules includes molecules of a target substance to be detected in said second plurality of molecules by said quasistatic spectral detection result, and wherein said first Raman signal detector is configured for detecting a relatively sparse subset of Raman scattering radiation frequencies in comparison to said second Raman signal detector. 
   
   
     9. The apparatus of  claim 2 , wherein said synchronous detector comprises one of a homodyne detector having a first reference frequency equal to said actuation frequency and a heterodyne detector having second and third reference frequencies that sum to said actuation frequency. 
   
   
     10. The apparatus of  claim 1 , wherein said actuation frequency is in a range of 1 Hz-100 MHz, and wherein said actuation device is selected from the group consisting of: surface acoustic wave actuators, piezoelectric actuators, microelectromechanical actuators, and microfluidic actuators. 
   
   
     11. A method for facilitating surface-enhanced Raman spectroscopy (SERS), comprising:
 receiving a plurality of analyte molecules for attachment near a SERS-active structure; 
 periodically deforming the SERS-active structure at an actuation frequency in a vicinity of the analyte molecules; and 
 receiving Raman radiation scattered from the analyte molecules at a synchronous measuring device that generates at least one Raman signal measurement therefrom, the synchronous measuring device being synchronized with said actuation frequency. 
 
   
   
     12. The method of  claim 11 , said synchronous measuring device comprising a Raman signal detector that generates at least one spectral detection result from said received Raman radiation, said synchronous measuring device further comprising a synchronous detector receiving said at least one spectral detection result and generating therefrom said at least one Raman signal measurement, said synchronous detector operating at said actuation frequency. 
   
   
     13. The method of  claim 12 , wherein said synchronous detector comprises one of a homodyne detector having a first reference frequency equal to said actuation frequency and a heterodyne detector having second and third reference frequencies that sum to said actuation frequency. 
   
   
     14. The method of  claim 12 , said at least one spectral detection result varying periodically at the actuation frequency according to said periodic deformations of the SERS-active structure and exhibiting at least one peak value within at least one peak interval of each period thereof, wherein said synchronous detector uses phase sensitive detection to detect said at least one spectral detection result during said at least one peak interval of each period thereof. 
   
   
     15. The method of  claim 12 , said at least one spectral detection result comprising a first spectral magnitude at a first Raman scattering frequency and a second spectral magnitude at a second Raman scattering frequency, each of said first and second spectral magnitudes varying periodically at the actuation frequency according to said periodic deformations of the SERS-active structure and respectively exhibiting at least one peak value within at least one peak interval of each period thereof, wherein said synchronous detector uses phase sensitive detection to detect said first and second spectral magnitudes during said respective peak intervals of each period thereof. 
   
   
     16. The method of  claim 12 , said Raman radiation, said SERS-active structure, and said plurality of analyte molecules being first Raman radiation, a first SERS-active structure, and a first plurality of analyte molecules, respectively, the method further comprising:
 detecting an optimal deformation amount for said first SERS-active structure based at least in part on said spectral detection result from said first Raman signal detector and said at least one Raman signal measurement from said synchronous detection device; 
 quasistatically deforming by said optimal deformation amount a second SERS-active structure similar to said first SERS-active structure near which a second plurality of analyte molecules is disposed; and 
 receiving second Raman radiation scattered from said second plurality of analyte molecules and generating therefrom a quasistatic spectral detection result; 
 wherein said first plurality of analyte molecules includes molecules of a target substance to be detected in said second plurality of molecules by said quasistatic spectral detection result. 
 
   
   
     17. The method of  claim 11 , wherein said actuation frequency is in a range of 1 Hz-100 MHz, and wherein said actuation device is selected from the group consisting of: surface acoustic wave actuators, piezoelectric actuators, microelectromechanical actuators, and microfluidic actuators. 
   
   
     18. An apparatus, comprising:
 a SERS-active structure near which a plurality of analyte molecules is disposed; 
 means for detecting Raman radiation scattered from said analyte molecules; 
 means for periodically deforming the SERS-active structure at an actuation frequency to cause an output of said means for detecting to be periodic at said actuation frequency; and 
 means for synchronous processing of said output of said means for detecting to generate therefrom a Raman signal measurement, said means for synchronous processing using a reference frequency equal to said actuation frequency. 
 
   
   
     19. The apparatus of  claim 18 , wherein said means for synchronous processing comprises one of a phase sensitive detection device, a homodyne detection device, and a heterodyne detection device. 
   
   
     20. The apparatus of  claim 18 , wherein said output of said means for detecting is selected from the group consisting of an energy of said Raman radiation at a single predetermined scattering frequency, an energy of said Raman radiation at a peak scattering frequency, and a combined spectral energy of said Raman radiation across a predetermined range of Raman scattering frequencies, wherein said wherein said actuation frequency is in a range of 1 Hz-100 MHz, and wherein said means for periodically deforming includes one or more of a piezoelectric actuator, a surface acoustic wave actuator, a microelectromechanical actuator, and a microfluidic actuator.